Measurement of the Radiative Width of theη′in Two-Photon Interaction at SPEAR

Abstract

Events of the type $e^{+}{e}^{-}\to e^{+}{e}^{-}{\eta }^{\prime }\mathrm{}\left(958\right)\mathrm{}$ have been observed with the Mark II detector at SPEAR by detecting the decay mode ${\eta }^{\prime }\to {\rho }^0\gamma$. From the observed cross section and known branching fractions of the ${\eta }^{\prime }$ is ${\Gamma }_{\gamma \gamma }=5.9\mathrm{}\pm 1.6\pm 1.2$ keV and the total width is $\Gamma =300\mathrm{}\pm 90\pm 60$ keV (statistical and systematic errors).